The present invention relates to digital imaging devices, and more particularly, to digital imaging devices that implement methods for transitioning from a displayable focus process to a high speed focus process, and for verifying focus, in a digital imaging device.
A typical digital imaging device may use a shutter release switch having at least two positions, referred to as S1 and S2. The preview mode may be initiated by depressing the shutter release switch to the S1 (preview) position. Taking a final photograph may be initiated by depressing the shutter release switch fully to the S2 (capture) position. The control that a photographer uses to initiate picture taking is referred to as a shutter release switch or button, even if the camera is entirely electronic and has no actual shutter mechanism.
There has been a strong desire to have imaging devices perform a focusing operation automatically based on the fact that the user simply points at an image scene. The drawback is that during this time the user is trying to compose the scene. Hence there is a need to have a continuous stream of images. This means that a “slow” focus rate is required because an image pattern that substantially covers the image sensor is being captured. Focusing using this continuous stream of images (continuous focus mode) is typically acceptable for liveview or video, but is not accurate enough for high resolution captured images. A problem also lies in the fact that user may want to capture an image before the focus process is completed. However, after pressing the shutter button to the capture (S2) position, there could be a significant delay. Thus, users of digital imaging devices are often annoyed by lengthy shutter lag times when taking pictures. Most of the lag comes from slow auto-focus times that occur after the users presses the shutter button to the preview (S1) position.
It would be desirable to have a solution to the problem of transitioning from a displayable focus process to a high speed focus process in a digital imaging device to minimize focusing delay time. It would also be desirable to quickly verify that the digital imaging device is in focus to avoid a long auto-focus delay.